berry



A. F. BERRY. CURRENT IND|CATOR.

APPLICATION FILED MAY 12, 1917.

Patented June 3 1919. 2 SHEETSSHEET I- Fig. 4.

U r. ,T B WE \C t@. r F v nu u T mm A, F. BERRY. CURRENT INDICATOR.

APPLICATION FILED MAY I2. 1917.

1,305,514. Patentedlune 3,1919.

2 SHEETS-SHEET 2.

Inventor: 'flrthur Francis Berrg 5 MQQWH;

H is 'fltcorneg. I w

ample as nickel when in use be shielded to a extentagainst the cooling action of surra ion.

CURRENTJNDICATOB.

' Specification of Letters Patent.

Application filed May 12, 191?. Serial No. 168,296.

To all whom it may con ern Be it known that I. Amm'n Fnaxcrs Bunny, :1 subject of the King of Great Britain and Ireland. residing at Ealing. in the county of li-Iiddlesex. Phig'land, have invented liiiprovements in or Relating to Current- Indicators, of which the following is a specification.

This invention has reference to electric current indicators designed to serve as fuses,

and it has for its object to provide improved constrin-tions of electric current indicators suitable for electric circuits of various kinds but particularly those intended for cooking. heating and like purposes, so that'it can be readily determim-d-at a glance whether the circuit with which the current indicator is associated is in action or not.

A current indicator device according to the invention so constructed. that when in '()l(llll2ll' use, a portion thereof intermediate of its ends is caused to l)(f(0lllt luminous by the current passing therethrough while its end portions. for remaincooler and relatively non-luminous. For this purpose a resistance conductor such as a resistance wire or strip 'made of small gage and of a metal or alloy. such for exchromium alloy. that is not readily fusible redness by an electric current. becomes coated with a protective insulating film of oxid, is so wound. bent or otherwise formed as to constitute one or more concentrated or lo calized intermediate portionsin which heat. due to the passage of an electric current of predetermined safe value therethrougrh, is allowed to develop sutiiciently to cause it or them to become luminous or glow while the remaining portions of the conductor wire are left sulliciently cool to prevent them be coming red hot .and luminous. To assistlin the production of a glowing heat in the said concentrated portion or portions (if resist.-

ance conductor. such portion. oreach of them whentwo or more are provided. may, greater or less rounding air. 'asdiy shielding means on the.

conductor or the' current indicator.liloelt or carrier. while the remaining portions of the current indicator are left freely exposed to the cooling action of air so as to he prerented froth becoming luminous.

(urrent indicators according to the in vention canbe variously constructed.

connection to terminals.

and which when heated to as shown, he formed with adapted to shield the central coiled portion In the ings. Figure 1 shows partly inside elevation and partly in vertical section and with part of the current indicator block broken away, a current indicator fuse constructed according to the invention. Fig. 2 is a plan of the current indicator withthe. cover shown in Fig. 1 removed. current indicator alone drawn to a still larger-scale. l igs. st and 5 are similar Views to Fig. 1. showing modified constructions. Figs. -(3. T. R and 9 are views showing other forms of current indicators according to the invention. Figs. 10 and 11 are two views showing another construction of current indicator according to the invention. The current indicators are "shown to. an enlarged scale for the sake. of clearness.

According to the constructionshown in Figs. 1. 2 and -3, the central portion of a length of tine wire or strip a of resistance accompanying illustrative draw- Fig. 3 is a view of the Patented June 3. 19191.

metal'or alloy such asreferred to. is coiled, 1

wire) being left straight. except it may be' the extreme end portions which may be coded to form eyes, to fit 0V0! terminal screws. or which. as shown, may be simply fixed in terminals I) fixed to a block or carrier of ordinary refractory insulating material such as porcelain.

a concave part d a of the current indicator to some extent from air currents and to reflect radiant heat received from such central portion back on to the same and so assist in its being raised to and maintained at a temperatur -eat which it will become luminous or glow.- Or, for

a like purpose. the block 0 may, as shown in Fig. 4-, be provided with a cup-like part c in which the coiled portion a indicator is placed and which has oppositely The block 0 may, f

of the current arranged slits or passages c through which v theend or side portions of the wire a extend. Tofurther shield the coiled portion (1 of the current indicator, the cup-like part 1' may. as shown. he provided with a cap-e formed with a viewing aperture Fig. 5 shows a current indicator provided with two coiled portions (4 each adapted device of which the fuse forms part, is in action.

Fig. '7 shows a current indicator compris ing a length of strip metal the central portion a of which is reduced in width, by stamping or cutting, to form the localized portion that will glow under the circumstances mentioned.

THE-concentrated or localized portion a of the current indicator can be shaped to give a (lot or dash of redness for the required indication when traversed by a predetermined safe working current.

If desired, the whole current indicator,

when mounted, may, as shown in Figs. 1 and 4, be. provided with a protective cover 7' hav-- ing an aperture at g through which the coiled portion a of the current indicator can be seen when glowing. Such a cover serves to protect the current indicator from external air currents, particularly if the block 0 be not provided With a cup-like part c for shielding the part a.

When current indicators of. the kind de scribed are used with heating devices of high and low hcatin value arranged in proximity to one: anot er, the apertures g in the covers 7' of the separate current indicators may be fitted with glass or mica windows of difierent colors, or be otherwise adapted, to indicate for example high and low heating values so that it can be readily seen when a heating device of high or low heating value is in use. Or the localized or glow portions of the current indicator may be shaped to give such indication, as illustrated for instance in Figs. 8 and 9, where resistance strip material is shaped, as by stamping, to form the glow portion a in the shape of the lcttersH and l. respectively to indicate high and low.

The current indicator blocks are shown in Figs. 1, at and 5 provided with plug connections h connected to the terminals b.

According to the construction shown in Figs. 10 and 11 the current indicator is built up of very fine wire a. ot the kind referred to, by winding the wire.v with the aid of a fornier, until a suitable number of strands or loops of convenient length are assembled as shown in Fig. 10 to suit the current to be carried. The requisite concentration of the intermediate or central portion of the fuse thus produced may then beobtaincd by twisting as a whole the central portion of the group of strands that are disposed parallel to one another in the act or winding. In this way there can be obtained a current indicator having, as shownin Fig, 11, a concentrated portion (/1 the parts which, being covered with a thin film of oXid when heated to redness previous to twistin that is to say, in the course 01": manufacture,

will be insulated from each other, and two enlarged end portions (4 each composedbl. a" number of turns of wire that may be spaced apart as shown, to allow of air entering freely between them to keep them cool. The end portions (6 serve for attachment to fuse terminals on a fuse block.

Current indicators constructed as described, have a very small voltage drop, a very small energy consumption and a small heating capacity which is localized.

What I claim is 1. An electric current indicator comprising a conductor having between its end portions a localized glow portion forming only a com niratively small part of the length of the conductor and adapted when traversed by an electric current, to glow, while its end portions remain cooler and rclativelynonluminous, and means arranged behind and in proximitv to said glow portion andhaving its front surtacc adapted to throw forward radiant energy received from said glow portion and ctmccntrate it on said glow portion. for the purpose set forth.

An electric current indicator comprising a conductor ha ving between its end portions it loculimd bent portion forming a small closely spaced bent mass oteonductoij constituting only a small part of the total length of the conductor and adapted to'glow and serve as a current indicator when traversed by an electric current, said conductor being formed of metallic resistance material having a high melting point and having thereon a protective insulating film of oXid, and means arranged behind and in proximity to said glow portion and having its front surface adapted to throw forward radiant energy received from said glow portion and concentrate it on said glmv portion for the purpose set forth.

3. An electric current indicator comprising a conductor made of oxidizahle metallic resistance material and having between its ends a portion thereof bent to a convoluted shape so as to constitute a minute concentrated portion of conductor of a length forming only a small fraction of the total length of the comluctor and adapted to admit of heat developing therein sull iciently to cause it to become luminous when traversed by an electric current while the remaining end portions of the conductor will remain sulliciently cool to prevent them becoming red hot, said convoluted portion having a. film of metallic oxid thereon, and a refractory body arranged in proxin'lity to and behinc said convoluted mass and having a concave approximately spherical front surface adapted to throw forwa rd radiant energy received from said mass and concentrate it on said mass for the purpose set forth.

4. An electric current indicator comprisihg a conductor having a small portion of its length adapted to form a bead or spot oflight while its remaining and longer end portions remain relatively non-luminous when traversed by an electric current and said luminous portion of conductor.

5. An electric current indicator comprismg a conductor formed of metallic resistance wire and having between its end portions, a coiled portion the convolutions of which are near together and each provided with a film of metallic ,oxid that separatesit'sidewise from adjacent convolutions, said coiled portion forming a'eoncentrated glow device constituting only a. small fractionof the length of the current indicator, and a refractory body arranged behind and in proximity to said coiled portion of said conductor and having on its front side a concave approximately spherical surface adapted to throw forward, heat and light energy received from said coiled portion of conductor and concentrate said energy on such portion of conductor forthe purpose set forth.

6. An electric current indicator having, a

small portion of its length between its end portions adapted to glow and form a, head or spot of light when traversed by an electric current while its remaining and longer end portions remain relatively non-luminous and means adapted to shield said glow portion to some extent against loss of heat while leaving the remainint end portions of said current indicator unprotected against loss of.

heat. a

7. An electric current indicator having a portion thereof adapted to form when in use, a localized luminous portion to serve as a current'indicator, and a cup like part in which the localized "luminous portion of the current indicator is placed and through side portions of which the cooler end portions of the current indicator pass.

8. An electric current indicator having a portion thereof adapted to form when in use, a-localized luminous portion to'serve as a current indicator, a cup like part in which the localized luminous portion is placed and throughside portions of which .the cooler end portions of the current indi-- cator pass and a cap secured over the cup like part'and provided with a viewing aperture.

9. An electric current indicator comprisinc a base, terminals carried thereby, a length of conductor connected between said teru'iinals and having a portion thereof adapted to form, when in use. a localized glow portion, a shield surrounding said glow portion and having a VlOW aperture therein and a cover. inclosi-ng said current indicator and having a view aperture therein, opposite that in said shield. I

qigned at London, England, this 18th day of April 1917.

ARTHUR r ANoIs BERRY. 

